The early detection of HIV infection in babies born to HIV infected mothers is very important for disease management, as well as interventional and psychosocial reasons. Although identification of the presence of HIV through in vitro culture of the virus, polymerase chain reaction (PCR) amplification of HIV nucleic acid sequences, and/or identification of HIV p24 antigen is the most definitive approach (1-3), these techniques are expensive and not widely available, particularly in developing countries.
The standard IgG antibody-based assays for HIV detection are not useful for early detection of HIV infection in babies because of the maternal antibodies present in babies blood. The presence of maternal antibodies can be detected up to 18 months or more postpartum in an infant's blood using most ELISA assays and immunoblot methods (4, 5). Moreover, there is some variation in the timing of detection or seroreversion, depending on which commercial ELISA assay system is used. However, the mean time to seroreversion in HIV negative babies (i.e., the reversion from being HIV antibody positive to HIV antibody negative) using the most sensitive ELISA kit available is 13.5(.+-.3.5) months using serum and 5.5(.+-.2.5) months using elution of dried blood spots (6).
Since it has been the general belief that maternal IgA and IgM antibodies do not cross the placenta, studies have been carried out to determine the usefulness of HIV-specific IgA and IgM class antibodies in early detection of infection. It has been suggested that HIV-IgA antibodies may cross the placenta (22). However, the procedures used in the studies carried out to date lack the sensitivity required for early diagnosis of HIV infection in infants (7-9). Thus, there remains a need for a sensitive assay method to detect HIV-IgA antibodies present in neonatal blood serum during the first few month of a child's life.